Upfront issue with saving changes

Hi, I have a site setup in a sub-folder of the root domain as a sandbox for client approval. Is there some issue with saving changes in upfront if it’s installed as described?

It will resolutely not save changes at all. I have uninstalled & re-installed upfront & fixer twice & it still shows the same behaviour. When I click on save, the linking dot icon appears, then it just says ‘there was an error saving’. If I then exit the editor, the changes have not been saved.